The patents to Smyers, Jr. et al., U.S. Pat. No. 3,535,479; Drane et al. U.S. Pat. No. 2,558,830 and Robison U.S. Pat. No. 2,456,994 disclose time delay pressure switches which open and close an electrical circuit in response to changes in pressure in a fluid conduit, in which the delay is attained either by bleeding air into the actuating chamber for the switch, or by bleeding pressure past a regulating valve to provide a delayed action and regulation of the speed of operation of a switch arrangement.
While such valves and systems have been satisfactory for the particular uses for which they have been designed, the check valve and system of our present invention is an improvement over the prior time delay systems in that a positive shut-off of fuel is attained for a Diesel engine upon loss in oil pressure in a far simpler manner than the prior art delays mentioned above, providing an effective, low-cost unit disconnecting the fuel supply valve after a positive shut-down, to prevent the battery from running down, and particularly adapted for an unattended engine in delaying opening of the fuel supply valve for at least 30 seconds as pressure decreases by bleeding the pressure down through a bleed tube leading through the check valve, from 8 psi to 5 psi in cooperation with an accumulator accumulating oil so at 8 psi, the pressure will bleed down to 5 psi and lower.
The advantages of the present invention, therefore, are that the effectiveness of the shut-off system is attained at a reduced cost by the passing of a bleeder tube through the check valve to bleed down the oil pressure as the engine stops or as there may be a leakage of oil, and by the provision of an accumulator in the valve chamber, and a pressure switch associated with the valve chamber, controlled by the accumulator and bleeder tube and opening at predetermined pressures to effect opening of the fuel shut-off valve and provide a delay in restarting the engine.
A further advantage of the invention is the provision of a simple and inexpensive time delay unit for Diesel engines disconnecting the fuel valve for the engine and preventing accidental restarting of the engine for a predetermined time delay interval.
A still further and important advantage of the invention is the control of a fuel shut-off valve of a Diesel engine by a normally open and a normally closed pressure switch in series and energizing a fuel shut-off valve to shut off the supply of fuel to the engine upon predetermined low pressure conditions in which the normally closed pressure switch opens and the normally open pressure switch closes on lower predetermined decreasing pressures to provide a time delay in opening of the fuel shut-off valve for restarting of the engine.
Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.